Mine roof support



Sept. 15, 1970 J, ov cs 3,528,253

MINE ROOF SUPPORT Filed March 13, 1969 2 Sheets-Sheet 1 INVENTOR. 44105 J. 4 0/1465 Sept. 15, 1970 L.J. KOVACS MINE ROOF SUPPORT 2 Sheets-Sheet 2 Filed March 13, 1969 INVENTOR 44Ja5 J. k owqcs BY J I J -M/IWL /6W United States Patent O 3,528,253 MINE ROOF SUPPORT Lajos J. Kovacs, Mansfield, Ohio, assignor to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Continuation-impart of application Ser. No. 692,847, Dec. 22, 1967. This application Mar. 13, 1969, Ser. No.

Int. Cl. E2111 21/00; E04b 1/48 U.S. CI. 61-45 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 692,847 filed Dec. 22, 1967 now Pat. No. 3,469,- 407 and titled Mine Roof Support.

BACKGROUND OF THE INVENTION This invention relates to mine roof support structures and particularly to shield assemblies having tandem expansion shells for supporting the mine roof.

In supports for mine roofs an opening is drilled ver tically into the roof and a bolt having a blind anchor for gripping the roof material is inserted into the opening. A roof plate is installed on the lower end of the bolt on the outside of the opening and against the surface of the roof. The bolt is turned to pull the roof plate into contact with the surface of the roof and the expansion shells or anchors are expanded into contact with the wall of the opening to hold the shield assembly in place and support the roof.

Such devices have not been particularly successful in supporting a mine roof consisting of layers or strata of soft material. Such roofs may have more than one layer of soft material or they may consist of alternating layers of hard and soft material. With the prior art devices there has been no assurance that such roofs will be adequately supported. Without adequate support of the mine roof, shoring or other devices must be utilized with the attendant increase in cost. Some of the prior art devices have utilized tandem anchors arranged on a single bolt, however these have not proven satisfactory in operation and have been relatively expensive thereby preventing their widespread use.

SUMMARY OF THE INVENTION It is therefore, an object of the present invention to provide an improved shield assembly for supporting mine roofs that is economical to manufacture and assemble. Another object of this invention is to provide a shield assembly consisting of a plurality of expansion shells secured to each other by an improved bail. A further object of this invention is to provide a shield assembly having a plurality of expansion shells arranged in tandem on a single bolt that will provide improved support for a mine roof of soft material.

This invention contemplates a shield assembly for a mine roof comprising a threaded bolt and a plurality of expansion anchors formed of complementary, elongated, generally semi-circular, opposed shells spaced along the 3,528,253- Patented Sept. 15,, 1970 ice bolt. Each anchor is provided with an expansion plug having a tapered exterior for separating the expansion shells when the expansion plug is drawn along or toward the bolt. The expansion plugs are secured to each other and at least one expansion plug is internally threaded with the bolt extending through the threaded expansion plug or expansion plugs. A U-shaped, elongated metal bail extends longitudinally between the anchors and over the upper end expansion plug and is secured to the lower end of each of the opposed shells. The U-shaped end of the bail may conform to the tapered exterior of the upper end expansion plug. If the bail conforms to the tapered surface of the upper end expansion plug, the expansion plugs need not be secured to each other but all of the expansion plugs must then be internally threaded with the bolt extending therethrough.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of the shield assembly of this invention with portions broken away;

FIG. 2 is a top plan view of the shield assembly of FIG. 1;

FIG. 3 is a cross sectional view along the line 33 of FIG. 1;

FIG. 4 is an elevational view of the expansion plugs for the shield assembly of this invention with a portion broken away;

FIG. 5 is an elevational view of an alternative embodiment of the shield assembly of this invention with portions broken away, and

FIG. 6 is a perspective view of the bail for the shield assembly of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIG. 1 wherein one embodiment of this invention is illustrated, reference numeral 10 denotes a shield assembly comprising a bolt 11, a first expansion anchor 12, a second expansion anchor 13 and a bail 14. The bolt 11 is threaded along at least a portion of its length and terminates at one end in a head 15. The threaded portion of the bolt 11 is of suflicient length to provide for axial movement of expansion plugs during expansion as will be hereinafter explained. A roof plate 16 is aflfixed to the bolt 11 and rests on the head 15.

In order to spread the expansion anchors 12 and 13 into contact with the wall of a roof opening (not shown) an expansion plug 17 is provided adjacent the upper end of the expansion anchor 12 and an expansion plug 18 is threaded onto the bolt 11 adjacent the upper end of the expansion anchor 13. The expansion plugs 17 and 18 are frusto-conical in configuration and they are provided with longitudinally extending slots 20 on opposite sides of each plug 17 and 18. Longitudinally extending guides 21 are formed on opposite sides of each of the plugs 17 and 1-8 and spaced approximately from the slots 20. The function of the slots 20 and guides 21 will be hereinafter explained.

The expansion anchors 12 and 13 are of identical construction and they comprise two laterally opposed, complementary shells 22. Each shell 22 is identical and semicircular in configuration with a longitudinally extending slot 23 extending from the upper end 24 of the shell to a point near the lower end 25 of the shell 22. Each shell 22 is provided with a recess 26 near the lower end 25 and a pivot means 27 on the other side of the shell. The recess and pivot means are complementary to provide for pivoting of the shells 22 during expansion and to align the shells 22 to the same axial point thereby promoting equal radial movement and loading of the shells as they are expanded. The upper end 24 of the shell 22 is provided with an inclined face 28 which with the inclined face 28 of its associated shell 22 defines an opening 29 for receiving the guide 21 of its associated expansion plug.

The bail 14 is an elongated U-shaped metal strap having a yoke 31 arranged over the expansion plug 17. The two arms 32 of the bail 14 extend along the outer sides of the shells 22 on opposite sides of the bolt 11. The arms 32 are received in the slots of the expansion plugs and the slots 23 of each of the shells 22. The bail 14 is secured to each of the shells 22 by ears 3-3 on the lower end of each shell which ears are deformed in conventional manner to grip the bail14.

In order to provide for expansion of the expansion anchor 12 in a customary manner, the expansion plug 17 is joined to the expansion plug 18 by a connecting member such as by a rigid tube 34 welded or otherwise secured to the lower end 35 of the expansion plug 17 and to the upper end 36 of the expansion plug 18. The expansion plug 17 is shown with a smooth bore 37 which bore may be eliminated, if desired. The expansion plug 18 is provided with a threaded bore 38 adapted to be threaded onto the upper end 40 of the bolt 11. The tube 34 functions to pull the expansion plug 17 toward the bolt 11 when the expansion plug 1 8 is drawn along the bolt in known manner, thereby insuring simultaneous expansion of the expansion anchor 12.

In the operation of the shield assembly 10 of this invention, the shield assembly is assembled with its components arranged as shown in FIG. 1. A sleeve 41 shown in phantom in FIG. 1 is slipped around the pair of lowermost expansion shells 22. The assembly 10* is inserted into an opening in the mine roof in the conventional manner. Upon insertion of the shield assembly into the opening in the mine roof, the sleeve 41 is removed. Alternatively, bolt 11 may be replaced with a threaded stud, shown in FIG. 1 as part 11, assembled on a lower bolt 43 by the use of a threaded coupling 42, shown in phantom in FIG. 1. After the shield assembly 10 has been placed in the opening, the head 15 of the bolt 11 is rotated causing the expansion plug 18 to be drawn along the bolt in the direction of the roof plate 16. Movement of the plug 18 pulls the expansion plug 17 toward the bolt 11 thereby forcing the expansion shells 22 of the expansion anchors 12 and 13 outwardly into engagement with the wall of the opening in a manner well known to those in the art. The shells 22 pivot outwardly about the recesses 26 and the pivot means 27 and engage the roof to hold the shield assembly within the opening and to pull the roof plate 16 into contact with the roof.

Referring now to FIGS. 5 and 6 wherein an alternative embodiment of this invention is shown, like reference numerals will be used to denote like parts as illustrated in FIGS. 1, 2, 3 and 4. The shield assembly of FIG. 5 comprises a bolt 51, a first expansion anchor 12, a second expansion anchor 13 and a bail 52. The bolt 51 is threaded sufiiciently for the movement of the expansion plugs during expansion of the shells and extends completely the shield assembly 50. The bolt 51 terminates at one end in a head 53, and is provided with a roof plate 16 resting against the head 53. An expansion plug 54 is provided adjacent the upper end of the expansion anchor 12 and an expansion plug 55 is provided adjacent the upper end of the expansion anchor 13. The expansion plugs 54 and 55 are frusto-conical in configuration and their exterior surface is substantially identical to the expansion plugs 17 and 18 and they are provided with longitudinally extending guides 56 and longitudinally extending slots 57. Both expansion plugs 54 and 55 are internally threaded in order that rotation of the bolt 51 will pull the two expansion plugs along the bolt in the direction of the head 53 forcing the expansion anchors 12 and 13 outwardly into contact with the roof opening in the same manner as the shield assembly of FIG. 1.

In order to maintain the expansion plug 54 in proper axial alignment with the expansion anchor 12 the bail 52 4 is provided with a reentrant portion 58 on each leg 60 of the bail 52 near the yoke 61. Upon assembly the reentrant portion 58 closely conforms to the taper of the expansion plug 54. The bail 52 is secured to the expansion anchors 12 and 13 by ears 3-3 in the same manner as the bail 14 is secured to the shield assembly 10 as shown in FIG. 1. For ease in factory assembly operations, the reentrant portion 58 of the bail 52 is substantially perpendicular to the yoke 61 and the legs 60 are bent outwardly away from the reentrant portion 58 when the bail is not attached to the expansion anchors 12 and 13.

The foregoing invention has been described with reference to the utilization of two expansion anchors. It should be understood that this invention may be utilized with equal facility where more than two expansion anchors are assembled on a bolt. Such as, for example, the shield assembly shown in my copending application.

It can be seen from the foregoing that the shield assembly of this invention provides an economical and readily assembled shield assembly and one in which the expansion plugs provide for simultaneous expansion of the expansion shells into contact with the wall of the opening in the mine roof. It should be understood that various modifications may be made in this invention without departing from the scope of the following claims.

I claim:

1. A shield assembly for a mine roof comprising a threaded bolt, a plurality of expansion anchors arranged in tandem, said anchors comprising complementary, elongated, generally semi-circular, opposed shells, a longitudinal slot in the upper end of each of said shells, said anchors being spaced along said bolt, an expansion plug for each anchor, each expansion plug having an annular part and a tapered exterior for separating said shells when said expansion plugs are moved relative to said bolt, at least the lowermost expansion plug having a threaded bore through which said bolt extends, a thin walled, cylindrical connector means secured at its ends to said expansion plugs, a bail for said expansion anchors comprising a U-shaped elongated metal loop extending longitudinally between the anchors and over the uppermost expansion plug, said bail having a yoke and a pair of arms extending therefrom, and means securing the lower ends of said opposed shells to said bail along opposite sides of each of said anchors, said bail being re ceived in said slots.

2. A shield assembly according to claim 1 wherein two expansion anchors are arranged in tandem.

3. A shield assembly according to claim 2 wherein the major portion of the upper expansion anchor is located above the upper end of said bolt.

4. A shield assembly according to claim 1 wherein the arms of said bail are substantially parallel to each other.

5. A shield assembly for a mine roof comprising a threaded bolt, a plurality of expansion anchors arranged in tandem, said anchors comprising complementary, elongated, generally semi-circular, opposed shells, a longitudinal slot in the upper end of each of said shells, an expansion plug for each anchor, each expansion plug having a tapered exterior for separating said shells when said expansion plugs are moved relative to said shells, at least the lowermost expansion plug having a threaded bore through which said bolt extends, a thin walled, cylindrical connector means secured at its ends to said expansion plugs, a bail for said expansion anchors comprising a U-shaped elongated metal loop extending longitudinally between the anchors and over the uppermost expansion plug, said bail having a yoke and a pair of arms extending therefrom, each arm of said bail having a reentrant portion extending from said yoke, and substantially conforming to the tapered exterior of said uppermost expansion plug, and means securing the lower ends of said opposed shells to said bail along opposite sides of each of said anchors, said bail being received in said slots.

6. A shield assembly for a mine roof comprising a threaded bolt; a plurality of expansion anchors arranged in tandem along said bolt; said anchors comprising complementary, elongated, generally semi-circular, opposed shells; a longitudinal slot in the upper end of each of said shells; an expansion plug for each anchor having an annular part, a threaded interior bore through which said =bolt extends and a tapered exterior for separating said shells when drawn along the belt; a bail for said expansion anchors comprising a U-shaped elongated metal loop extending longitudinally between the anchors and over the uppermost expansion plug; said bail having a yoke and a pair of arms extending therefrom; each arm of said bail including a reentr-an-t portion extending from said yoke and substantially conforming to the tapered exterior of said uppermost expansion plug to locate said uppermost expansion plug relative to its associated expansion anchor; and means securing the lower ends of said opposed shells to said bail along opposite sides of each of said anchors; said bail being received in said slots.

'7. A shield assembly according to claim 6 wherein two expansion anchors are arranged in tandem.

References Cited UNITED STATES PATENTS 1,666,805 4/ 1928 Williams 85-79 X 2,139,167 12/1938 Marshall 85-69 X 2,647,431 8/ 1953 Lewis 85-75 FOREIGN PATENTS 231,847 8/ 1956 Australia. 84,937 1/ 1955 Norway. 196,342 5/1965 Sweden.

16 DENNIS L. TAYLOR, Primary Examiner US. Cl. X.R. 85--67, 69 

